Containers that can simultaneously dispense more than one sort of fluid are desirable, especially when the fluids to be dispensed contain some active ingredients that are incompatible when these ingredients are mixed together in a single solution, yet it is desired to dispense both fluids with their active ingredients simultaneously. Several problems have consistently shown up with such dispensing systems. Venting of the containers, without allowing leakage of the fluid contents of a container, has been a consistent and recognized problem. An unaddressed problem with such a dispensing system is achieving and maintaining constant flow rates from the different containers (the result of unequal flow being the exhaustion of one container while another still contains fluid) so that the fluids dispensed are dispersed in an equal (or pre-determinedly different) ratio.
The importance of dispensing certain fluids from different containers for a particular effect or use has long been recognized. U.S. Pat. No. 1,134,098, to Bloch, "Perfume Sprayer" discloses a direct-action compression pump for spraying two perfumes simultaneously from two containers through two nozzles. The patent states that this system can produce fragrances not possible with single solution perfumes. This sprayer has venting of a different sort: air is compressed by the pump and passes through "vent" holes into the containers. The pressure created drives liquid up the dip tube and out into the atmosphere.
Various types of devices exist that allow two fluids to be dispensed from a single dispenser--either sequentially or simultaneously. U.S. Pat. No. 4,925,066 to Rosenbaum, entitled "Combined Sprayer and Refill Container," provides for a second container which attaches to a single container dispensing assembly. The auxiliary container is intended to hold a refill concentrate for replenishing the primary spray container. The patent is silent on the need for venting.
U.S. Pat. No. 5,152,461 to Proctor, "Hand-operated Spray With Multiple Fluid Containers" discloses a sprayer which has two fluid containers from which fluids are drawn through dip tubes up into a single trigger-activated pump, inside of which the fluids are mixed and from which they are dispensed through a single nozzle. The containers are individually vented through vent holes having one-way flexible valving mechanisms.
U.S. Pat. No. 3,786,963 to Metzler III, "Apparatus For Dispensing Mixed Components" discloses a dispensing apparatus having two dip tubes which are of unequal size and enter a fluid transfer channel below a trigger activated pump at spaced-apart locations. The patent is silent on the reasons for these differences. The apparatus has a vent hole opening into the pump chamber but the patent is silent on venting into the containers which would be used with the apparatus.
U.S. Pat. No. 5,009,342 to Lawrence et al, "Dual Liquid Spraying Assembly" discloses an assembly for dispensing different liquids made up of two or more liquid compartments, a spray pump dispenser, means for transferring the liquid to the pump, and a valve assembly for selecting one or another of the liquids or a mixture of the two for dispensing. The valve assembly is made up of to two major components; a central part having a liquid channel that can connect either or both of the inlet openings into the liquid compartment with the outlet into the pump and a control part for positioning that central part apparatus. Mixtures are created by the relative degree of openness of the inlet openings much in the way different degrees of warm water is produced by varying relative openings of hot and cold water faucets. The patent is silent on the need for venting.
U.S. Pat. No. 4,355,739 to Vierkotter "Liquid Storage Container" discloses a liquid container having two separate chambers each having a take-up tube that leads to a fluid transfer channel which is connected to a single spray pump. A moveable selector can be rotated to vary the size of the passageways between the take-up tubes and the fluid transfer channel and this varies the ratio of the liquids dispensed. The take-up tubes have one way valves to prevent reflux and the venting of the containers occurs through the connection area between the pump housing and the top of the container.
The need to vent a rigid container from which fluid is being dispensed is known. One example is U.S. Pat. No. 5,192,007 to Blomquist "Valve Assembly for Inverted Dispensing From a Container with a Pump" discloses a valving mechanism for dispensing a liquid from a single container, the mechanism having a vent passage and a liquid passage, both of which are provided with ball check valves. The vent valve is closed by the ball when the container is inverted during dispensing. However, when sufficient negative pressure differential is developed within the emptying container, the ball unseats itself and allows ambient air to enter the container.
However, the prior art has not recognized the necessity of a precise balancing of the venting of the containers for a dispensing system made up of multiple containers with a single pump and dispensing nozzle, to consistently dispense the desired ratio of fluids.
Venting a single container is a simple matter, and even if the venting system is not properly designed, causes no worse problems than inefficient or irregular pumping of fluid from the container. But when a single pump is drawing fluids from more than one container, unequal venting causes serious functional problems.
As stated before, the reason for having multiple container systems is to allow simultaneous dispensing of two (or more) distinct fluids. One fluid might be water and the other a concentrate (the use envisioned by U.S. Pat. No. 5,152,461). Or one container might hold a fluid with an active ingredient which the fluid in the second container would deactivate. Examples of such pairs of fluids could be a cleaning composition and a bleach, or a pair of stain removing compositions, one an aqueous composition and the other a high-solvent level enzyme containing composition.
Whatever the pair of fluids are, they are intended to be dispensed simultaneously and in a fixed ratio to each other (the ratio being set either by the design of the system itself, as discussed below or by some sort of flow adjustment means (U.S. Pat. No. 5,152,461 discloses one type of variable flow control mechanism)).
As a pump draws fluid from a rigid container, the fluid drawn from that container must be replaced by air (venting) for pumping to continue. (Non-rigid containers simply collapse as fluid is drawn from them). When a single pump draws fluids from two containers simultaneously, and especially when the fluids being pumped from the different containers have different vapor pressures, the degree and speed of venting of the two containers must be almost exactly the same, or a pressure differential is created between the two containers. This pressure differential causes fluid to be pumped from the two containers at different rates, which tends to exacerbate the pressure differential. It has been found that the "replacement" speed of the venting of the container must be almost instantaneous to avoid the creation of this pressure differential/ratio problem. The result of this is that the desired ratio of the two fluids is not dispensed.
Manually operable pumps for use by individuals in any location are necessarily small and light--and therefore have low displacement capacities and low pressure differentials. Available trigger operated spray pumps have been found to pull pressure differentials below approximately 8 psi (550 millibars).
When fluids are dispensed from the fluid containers, a small pressure differential can form without unimpeded and instantaneous venting of the containers in a multiple component dispensing system, making the venting a critical factor. With larger capacity higher pressure differential pumps, flapper valves, ball check valves, duck bill valves or the like covering the vent holes would pop open promptly in response to the action of the pump which created the pressure differential pull. But small pressure differentials mean that small differences in the behavior of the materials or components of a venting system can produce unbalanced venting. For example, deformable materials for use in components of items for mass consumer use are neither precision formulated nor configured. Thus, one flapper valve of a pair might be more or less rigid than the other, and one would flex open in response to a small pressure differential pull before the other, creating unequal venting with the problems described before.
The obvious solution to instantaneous venting is simply to have permanently open vent holes into the fluid containers. This, however, is not a functionally acceptable solution for such a dispensing system, for the simple reason that such vent holes would also be leak holes. Fluid leakage through open vent holes would occur when such containers are inadvertently inverted or knocked on their sides. Leakage would also occur if such containers were transported in a low-pressure environment (e.g. the cargo section of an airplane). Additionally, permanently open vent holes would allow vaporization of volatile compounds from within a fluid container. Thus, some means of closing the vent holes is necessary, but the closure mechanism must not in any way impede the flow of air into the container.
While consistency of dispensing is controlled by the venting mechanism of the dispensing apparatus, the ratio of the liquids to be mixed and then dispensed is controlled by the intentional balancing of several interrelated factors: the length and diameters of the dip tubes, and the viscosities and specific gravities of the fluids to be dispersed, as well as the pumping capacity of the pump.
Another thing that must be prevented for consistent dispensing of two distinct fluids is excessive commingling of the fluids before they are dispensed. This can happen either because the two fluids are brought together in a larger than necessary fluid transfer channel or because a pressure differential created between the containers will cause siphoning between the containers. To prevent this, some sort of balanced one-way valving system must be incorporated into the fluid system of the assembly.
Accordingly, it is an object of the invention to provide a multiple container dispensing assembly having multiple fluid containers connected to a single pump and nozzle dispensing system which allows balanced pumping of fluid from each container so that the desired mixture of fluids dispensed is always maintained.
It is a further object of this invention to provide such a dispensing system that achieves that stable ratio of dispensing fluids by means of a venting system that allows simultaneous and instantaneous, non-impeded venting of the containers to the ambient atmosphere.
Another object of the invention is to provide such a dispensing system that can be transported and stored without danger of leakage or vaporization of its contents.
Yet another object of the invention is to provide such a dispensing system that will disperse a mixture of two or more different fluids in a specific and pre-set ratio.
A further object of the invention is to provide such a dispensing system that will prevent premature commingling or siphoning of the distinct fluids to be dispensed.